Apparatus for controlling burners



p 193in. G. SPAHR 1,878,010

APPARATUS FOR CONTROLLING 'BURNERS Filed June 1 1925 2 Sheets-Sheet l \SUPPLY C/Rcu/T L /Z Fun! Burro/v ATTOR/Vfm Sept. 20, 1932. D. G. SPAHR APPARATUS FOR CONTROLLING BURNERS Filed June 19. 1925 2 Sheets-Sheet 2 i V m A VIIIl/lllllllll/llll/Ifl/lIII/I/l/lllIf/I/l/l/l/llIII/Ill! Patented Sept. 20, 1932 UNITED. STATES PATENT OFFICE DION G. SPAHR; OE MINNEAPOLIS, MINNESOTA, ASSIGNOR, BY MESNE ASSIGNMENTS,

'IO MINNEAPOLIS-HONEYWELL REGULATOR COMPANY, OF MINNEAPOLIS, MINNE- SOTA, A CORPORATION OF DELAWARE APPARATUS FOR CONTROLLING BUR-NERS Application filed June 19,

This invention relates to new and useful improvements in the method of and apparatus for controlling burners. While capable of various adaptations as will be observed, this invention readily lends itself to the fluid fuel burner art Whether gaseous or liquid. In this art, it is essential to prevent the supply or flow of the fuel to the burner upon failure of combustion and it is relatively immaterial whether such failure of combustion is initial or intermediate. In the case of gaseous fuel the disadvantages and dangers of the escape of unconsumed gas are obvious and in the case of liquid fuel, such as the common fuel oil, the outpouring of the unconsumed oil from the burner is injurious per se to burner surroundings in addition to the inherent danger of fire or explosion attendant upon the escaping oil.

In this art various devices and mechanisms have been and are employed to prevent such occurrences. These so-called safety devices take the form of drip-buckets, thermostatic devices operable by heat of combustion and pressure-actuated devices operable by expansive pressure in the burner chamber attendant upon combustion. These devices are operable to open or close the electric circuits to the burner or to shut-off fuel, valves, etc. The lever arm and drip-bucket combination is somewhat slow in operation and liable to accidental tripping while the other types in use are subject to variations in operative temperatures and pressures depending upon different types of burner installations with which the controls are to be used.

This invention provides a new and improved process and apparatus for controlling burners through the application, as a control medium, of differences in the light in the burner. This control is effected through electrically responsive devices whose resistivity is affected by light such, for example, as a selenium cell. A selenium cell has a resistivity when dark which makes the cell substantially a non-conductor of electricity and, when subjected to light, its resistivity is greatly decreased to convert it into substantially an electrical conductor. By positioning and protecting the selenium cell so that 1925. Serial No. 38,322.

it is subjected only to the presence or absence of light from the combustion of the burner, its functioning as a control medium is posi tive and certain.

The object therefore of this invention is to provide a process and apparatus for con trolling burners.

Other objects of the invention will more fully appear from the following description and the accompanying drawings and will be pointed out in the annexed claims.

In the drawings there has been disclosed a structure designed to carry out the various objects of the invention, but it is to be understood that the invention is not confined to the exact features shown as various changes may be made within the scope of the claims which follow.

In the drawings:

Figure 1 is a wiring diagram of an apparatus embodying the invention;

Figure 2 is a longitudinal section of a selenium cell and one form of mounting;

Figure 3 is a view in side elevation of the automatic cut-out mechanism; and

Figure 4 is a perspective view of the engaging portions of such mechanism.

This novel process and apparatus is disclosed in conjunction with a thermostat and relay mechanism to turn on and shut off the supply of electric energy from the main supply lines 11 and 12 of the motor 13. This motor is adapted to drive a centrifugal burner head or a blower to jet fuel oil to the bumer head as is now well-known. This thermostat and relay mechanism here shown is substantially the same as that shown in the pending application of Frederick S. Denison, Serial Number 7 22,586, filed June 26, 1924 and will be initially described.

The thermostatic element or thermobar comprises a substantially ring-like bar 14 which has securely attached thereto as by welding a relatively stiff metallic member such as the blade 15 formed of a bar of suitable metal which is an electric conductor. As the mechanism is preferably mounted in an upright position, the blade 15 depends from the thermo-bar 14. This ring-like'bar 14 is mounted, as is usual, in insulated relation.

Two terminals are supported adjacent the bar 14 and are here indicated as termlnally pointed contacts 16 and 17. The contact 16 is electrically connected to the wire 18 and the contact 17 is so connected to the wire 19.

A single control circuit is preferably used and it may be closed across the contacts 16 17 and, in the form shown, the c1rcu1t-closing means consists of a pair of members adapted to be successively engaged wlth their respective contacts. The relatively stiff blade 15 is carried by the thermo-bar 14 and is adapted to engage the contact 16 in order to form an electrical connection therewlth. A second blade 21 is also carried by the thermo-bar 14 by means of its riveting to the blade 15. The blades 15 and 21 are so arranged that they terminally diverge and each bears a contact tip 22. The contact tip of the flexible blade 21 is adapted to engage the end of the lower contact 17 This flexible blade 21 is also provided with an aperture 20 so that the other contact 16 may freely be passed therethrough, the resultant air gap providing sufficient insulation between the contact 16 and the flexible blade 21. This flexible blade is also desirably provided with a reinforcing or backing plate 23. The upper ends of the backing plate, the flexible blade 21 and the relatively stiff blade 15 are riveted together to present a substantial- 1y unitary structure in electrical connection at that end. The plate 23 and blade 15 are both of relatively stiff metal and are disposed in terminally diverging relation, the flexible blade being interposed so that its flexibility permits movement of its major portion between the backing plate and blade 15. It may also be noted that the backing plate is provided with an aperture similar to the blade 21 for the same purpose. In addition to the thermostatic circuit wires 18 and 19, which are respectively connected to the contacts 16 and 17, a supplemental wire 24 is electrically connected to the thermo-bar 14 and, hence to the blade 15 and blade 21.

The switch forming the subject-matter of the previously cited pending application may next be described in conjunction with its connections. The switch is preferably borne by a panel usually mounted in a vertical position. An electro-magnetic coil 25 is mounted thereon to attract, when energized,

. an armature 26 having a weighted portion 27 and mounted upon a pivot pin 28. This armature lever has an arm 29 projecting beyond the pin 28 to engage and normally uphold a counterweight 31 connected to the parallel switch arms 32 each bearing a contact tip 33 for electrical engagement with the relatively fixed terminals of the main lead wires 34 and 35 from the supply lines 11 and 12. These switch arms are pivotally mounted upon the pivot posts 36 and the counterweight 31 normally tends to retain each lap 33 in contact with the respective terminal contacts 37 of the lead wires 34 and 35, the closing movement being limited by the adjustable screw 38. Upon closure of these switch arms 32, electrical energy passes from the line 12 to the lead wire 35 to contact 37 to switch-arm-contact 33, through the switch arm to post 36 and by wire 41 to the device to be energized such as the burner motor 13, and thence returns by the wire 42 to the other post 36, other switch arm 32, contacts 3337, wire 34 to the other supply line 11.

Thus, the counterweight 31 constantly exerts a gravitational force tending to hold the switch arms 32 in closed position. But, the armature weight 27 which exerts a greater force overcomes the force of the counterweight 31 and normally holds the switcharms in open position. However, upon energization of the electromagnet 25, the force of the weight 27 is removed, and the counterweight may close the switch-arms where they remain until the electromagnet is de-energized whereby the weight 27 may indirectly open the switch-arms.

The energization and de-energization of this electromagnet is effected by means of the thermostatic mechanism above-mentioned. The two-switch-arms 32 are conventionally represented as tied together by the bar 43 because they function as a unit in pivotal movements upon their posts 36. The electromagnet 25 is in series with the wire 18 which is terminally connected to the secondary side of a transformer 44 which has its primary constantly energized by its shunt circuit 4546 from the lines 34-35. The wire 19 leads from the other end of the secondary of this transformer to the thermostat contact 17. In the wiring diagram, the parts are represented in the positions occupied when the blower-motor is shut-off and the thermostat, usually positioned in the room or place to be heated, is warm enough to hold the blades from circuit-closing position so that the electromagnet circuit is open at the posts 16 and 17. As the thermo-bar cools, the blades 15 and 21 and the backing plate 23 move towards the contacts 16 and 17. Owing to the divergent relation of these two blades, the relatively flexible blade 21 first engages the lower contact 17 In such position, the upper contact 16 is freely passed through the alined apertures in the plate 23 and blade 21 and is out of electrical connection therewith While the other blade 15 is spaced from its contact 16. The electromagnet circuit thus remains open, being broken at the posts. Further movement of the cooling thermo-bar causes engagement of the stiff blade 15 with its 'contact 16. The backing plate its 1 spaced relation from the blade 15 while the blade 21 flexibly remains in contact with its contact 17. Thus, the contacts are successively made and the electro-magnet circuit 1s closed across the contact screws so that the electro-magnet is energized, its armature weight 27 is raised which permits the Weight 31 to drop and thus to movethe swltch arms into position closing the main line c1rcu1t to the motor. One of the switch arms carries a short arm 47 which is electrically connected to the wire 18 leading from the electromagnet to the contact 16. This arm 47 is adapted, when the switch-arms are closed, to effect electrical engagement with the relatively fixed contact 48 which is connected by the wire 24 to the thermo-bar 14. Thus, when the switch-arms are moved to circuit-closing position, the arm 47 cuts out the portion of the wire 18 connecting the post 36 and the contact 16 of the thermostat. This condition obtains so long as the electro-magnet 25 remains energized and any accidental break in the current from the main line will deenergize the electro-magnet and cause the motor circuit to be opened by force of gravity acting through the weight 27 which is heavler than the counterweight 31 and is therefore able to open the switch-arms against the pull of the weight 31.

However, disregarding such abnormal or accidental condition, the motor-sWitch-arms may be caused to be opened by movement of the thermo-bar 14 when it becomes heated and successively moves the blades 15 and 21 from their contacts. The circuit is not interrupted until the thermo-bar has moved a predetermined distance from the contacts. Such lag inthe breaking is provided by the use of the relatively stiff and flexible contact blades and the supplemental connection for the thermobar and blades. Thus, as the heating thermobar moves from the contacts, the stiff blade 15 is first disengaged from its post 16 and in such position, the contact 16 and that section of its wire 18 up to the supplementary switch arm 47- is de-energized but, the circuit from the electromagnet is maintained aci oss the arm 47, fixed contact 48 and wire 24 to the thermo-bar 1'4 and flexible blade 21 to the lowercontact 17 and wire 19 back to the eiectromagnet 25. The leads from the supply or power lines are thus maintained closed and supply electrical energy to the motor. When the thermo-bar has continued its opening movement for the predetermined distance or lag, the flexible blade is moved from its contact 17 and the circuit is opened. The relatively stifi' metallic backing plate 23 being movable with the blade 15 assures the opening travel of the flexible blade 21 in timed relation to that of the stiff blade 15.

When the electromagnet circuit is thus opened, the armature weight 27 drops and,

through the lever 29, rocks the lighter counterweight 31 of the switch-arms, moving the latter as well as the short arm 47 to open po sitions for a subsequent cycle of operations.

This novel process and apparatus forming the subject-matter of this invention may be employed in conjunction with the above thermostatic control mechanism which is in present commercial use as well as with other types but, as before stated,- for purposes of explanation, it will be described and its operation pointed out in connection with the above mechanism.

In the specific embodiment here shown, the burner-motor circuit has preferably two intermediate portions in parallel. A circuitbreaker is provided with suitable connections electrically associated with one of said portions and is adapted to open the motor circuit upon passage of current through such circuit-breaker connection for a predetermined interval. A circuit-closer is also provided for this same connection and is adapted to shunt out the circuit-breaker when normal conditions of burner combustion obtain. The control medium for this circuit-closer is a device responsive to conditions of the presence or absence of light, as for example, from the burner. This device which is electrically non-responsive when dark but in electrically responsive when receiving light is provided with connections electrically associated with theother of said parallel portions and is adapted, when receiving light from the burner to move the circuit-closer to closed position whereby the circuit-breaker is shunted out and rendered inoperative to open the burner motor circuit. Thus, for example, when the thermostat calls for heating operation of the burner motor and combustion properly takes place, the device will be subjected to light and will shunt out the circuitbreaker and permit normal running operation of the burner motor. Further, if combustion fails for any reason, the device will be rendered inoperative and the circuit-breaker will not be shunted out and will pursue its automatic function of interrupting the motor circuit.

The parts will be described more particularly with reference to the diagram of Figure 1. The parallel portions of the motor lines 4142 have each a transformer 50 and 51, respectively. The secondary 52 of the transformer 50 has a wire 53 leading therefrom to a post 54 to which is also connected the heating coil 55 having its other end connected to the post 56. I The post 56 is also connected to the transformer secondary 52 by the wire 53. This heating coil is placed about a thermo-bar 57 which is supported at one end of the bracket 58 of a switch support 59. The screw 61 afi'ords means for adjusting the position of this thermo-bar. The outer or free end of the thermo-bar has a reducedportion forming a tab 62 which is adapted normally to be received within an angular terminal recess 63 in the depending offset end 64 of the movable arm 65 of the circuitbreaker. This arm is flexible and is riveted to the offset conductor strip 66 connected to the post 67 insulated from the support 59. The free end of this arm 65 carries a contact 68 adapted normally to engage the complementary contact 69 held in relatively fixed position upon the offset end of the conductor strip 71. This strip is electrically carried by the post 72 insulated from the support 59. These two posts 67 and 72 are electrically connected in series with the wire 19 which leads from the post 17 to the transformer 44 so that the normal engagement of the two contacts 68 and 69 of the circuitbreaker does not interrupt the thermostatic control circuit at the wire 19. This circuitbreaker is so constructed and arranged that, upon the passage of current through the heating coil 55 for a predetermined interval, the thermo-bar 57 will be warped out of enga ement with the offset end 64 of the mova le arm 65 which is mounted so that its inherent resilience will cause the arm 65 to assume the position shown in Figure 3 with the result that the movable contact 68 is moved from the contact 69 and the thermostatic circuit is broken across the wire 19 and the relay or electro-magnet 25 is de-energized and the motor circuit is broken at the switch arms 32. The apparatus can only be re-conditioned for normal operation by the manual re-setting of this circuit-breaker arm such, for example, as by a push-button 73.

The selenium cell and associated parts function, upon closing of the motor circuit and proper ignition and combustion of the burner, to prevent this circuit-breaker from completin its timed operation by shunting out the eating coil 55. A wire 74 leads from the post 56 to a fixed contact 75 while a wire 76 leads from the post 54 to the fixed accordance with galvanometer contact 77. These two contacts may be bridged by a circuit-closer 78 operable by the movable coil of a sensitive relay of the galvanometer type having a core 79. A magnetic flux, to move the coil, may be set up by the coil 81 wound about the core 79 in practice. This coil 81 is in series with the wire 82 leading from the secondary 83 of the transformer 51 to the terminal 84 of the selenium cell 85, of common construction. The other terminal 86 of this cell is connected by the wire 87 to the other side of the transformer secondary 83. Therefore, when the motor circuit is closed, the secondaries 52 and 83 are energized, and current tends to flow in the selenium cell circuit and, if combustion does take place and light is cast upon the selenium cell, its resistivity is decreased thereby so that it substantially becomes a conductor and the sensitive relay in series therewith is energized so that the circuit-closer 78 moves to the dotted line position shown whereby the circuitbreaker resistance or heating coil is shunted out before its thermo-bar 57 has heated sufficiently to interrupt the thermostatic control circuit with its attendant interruption of the motor circuit. This thermostatic circuitbreaker is so constructed that the predetermined interval which must expire before the contacts 68 and 69 are opened is sufficiently long to permit normal ignition of the burner by any of the means commonly employed and the production of light to affect the selenium. When combustion or ignition does not nor-, mally take place, the selenium cell remains dark when its resistivity is so high as to prevent the passage of current to operate the sensitive relay with the result that the circuitcloser 78 remains in its normal full-line open position shown in Figure 1 and the circuitreaker performs its function of opening the coilitrol circuit after a predetermined interva In Figure 2 is shown one form of operative mounting for the selenium cell as used in this novel process and apparatus. Therein, the cell is shown as carried by a cap 91 secured to the outer end of the tube 92 so as to prevent entry of light to the cell. The tube opens at its inner end into a portion of the combustion chamber or adjacent the burner so that light from combustion adjacent the burner will affect the cell. As shown the tube is held by bolted lugs 93 to a portion 94 of the burner housing such as that found in a domestic heatin plant 95.

Pre erably, heated air currents are prevented from passing within the tube by means of a translucent partition 96 completely sealing the .burner end of the tube. This partition is preferably of relatively thick glass of red color. The portion of the tube adjacent the cell may be vented by the air-circulation inlets and outlets 97 and 98 which may be suitably trapped as shown to prevent entry of light whereby the cell is made solely responsive to burner light.

Having thus described my invention what I claim'as new and desire to secure by Letters-Patent, is:

1. A device of the class described, including a combustion chamber, a burner motor and supply circuit therefor, a thermostatically operable device connected for controlling the motor circuit, including a heating coil in a circuit associated with-the motor leads, a shunt-circuit for the heating coil, :1 relay-switch for controlling said shunt-circuit, a selenium cell disposed to receive light only from the combustion chamber, and a circuit associated with the motor leads, in which circuit said cell and relay-switch are connected in series.

2. A device of the class described, including a burner motor and supply circuit therefor, said circuit including a relay operated switch and circuit therefor, a circuit-breaker in said relay circuit, including a heating coil, a shunt-circuit for the coil, a relay-switch controlling the shunt-circuit, and a selenium cell connected in said shunt-circuit in series.

3. In a burner controlling apparatus, the

combination of an electrically operable burner having a circuit with a source of electrical energy, a circuit breaker having con-' operation of the burner, electrica energy is supplied the burner and upon failure thereof the su ply of said energy is interrupted.

4. n a burner controlling apparatus, the combination of a burner motor having a circuit connected to a source of electric energy, said circuit having two intermediate portions in parallel, a circuit-breaker having connections electrically associated with one of said portions and adapted to open the motor circuit upon passage of current for a predetermined interval through said circuit-breaker connection, a circuit-closer for said connections and adapted to shunt out said circuit-breaker, and a device electrically nonresponsive when dark but electrically responsive when receiving light and having connections electrically associated with the other of said parallel portions and adapted, when receiving light from the burner to move said circuit-closer to closed position.

5. In a burner controlling apparatus, the combination of a burner motor having a circuit electrically connected to a source of electric energy, the circuit having two intermediate portions in parallel, a transformer in each parallel portion, an electric circuit connected to the secondary of each transformer, a circuit-breaker operatively associated with one of said secondary circuits and adapted to open the motor circuit upon passage of current for a predetermined interval through said secondary circuit, a circuit-closer for said secondary circuit and adapted to shunt out said circuit-breaker, a device electrically non-responsive when dark but electrically responsive when receiving light inserted in the other of said secondary circuits and adapted when receiving light from the burner to move said circuit closer to closed position.

6. A device of the class described, comprising a tubular member closed by a cap,-carrying a selenium cell at its inner side, and a transparent partition element arran d within the tube between the open end 0 the tube and the cell, said tube, between said transparent element and cell, having a trapped vent passage, and an air intake passage.

7 The combination of a furnace with means for supplying fuel thereto and a circuit including a relay and a light sensitive electric cell exposed to the light rays from the furnace for shutting ofi' said fuel supply devices when the furnace flame goes out.

8. The combination of a furnace with means for supplying fuel thereto, an electrically actuated time limit cut-o'fi for said means, and a circuit including a relay and a light sensitive electric cell exposed to the light rays from the furnace for rendering said cut-oif inoperative upon the occurrence of successful ignition within the time period.

In witness whereof, I have hereunto set my hand this 12th day of June, 1925.

mono. SPAHR. 

